RESUMEN
Treatment with abiraterone acetate and prednisone (AA/P) prolongs survival in metastatic castration-resistant prostate cancer (mCRPC) patients. We evaluated the genetic variation in CYP17A1 as predictive of response to AA/P. A prospective collection of germline DNA prior to AA/P initiation and follow-up of a mCRPC cohort was performed. Five common single-nucleotide polymorphisms (SNPs) in CYP17A1 identified using a haplotype-based tagging algorithm were genotyped. Clinical outcomes included biochemical response and time to biochemical progression on AA/P. Logistic regression was used to assess the association between tag SNPs and biochemical response. Proportional hazards regression was used to assess the association between tag SNPs and time to biochemical progression. Odds or hazard ratio per minor allele were estimated and p-values below 0.05 were considered statistically significant. Germline DNA was successfully genotyped for four tag SNPs in 87 patients. The median age was 73 years (54-90); the median prostate-specific antigen was 66 ng/dL (0.1-99.9). A single SNP, rs2486758, was associated with lower odds of experiencing a biochemical response (Odds ratio 0.22, 95% confidence interval 0.07-0.63, p = 0.005) and a shorter time to biochemical progression (Hazard ratio 2.23, 95% confidence interval 1.39-3.56, p < 0.001). This tag SNP located in the promoter region of CYP17A1 will need further validation as a predictive biomarker for AA/P therapy.
Asunto(s)
Acetato de Abiraterona/uso terapéutico , Antineoplásicos/uso terapéutico , Neoplasias de la Próstata Resistentes a la Castración/tratamiento farmacológico , Neoplasias de la Próstata Resistentes a la Castración/genética , Esteroide 17-alfa-Hidroxilasa/genética , Anciano , Alelos , Progresión de la Enfermedad , Genotipo , Humanos , Estimación de Kaplan-Meier , Modelos Logísticos , Masculino , Persona de Mediana Edad , Oportunidad Relativa , Polimorfismo de Nucleótido Simple , Prednisona/uso terapéutico , Modelos de Riesgos Proporcionales , Estudios Prospectivos , Antígeno Prostático Específico/sangre , Neoplasias de la Próstata Resistentes a la Castración/mortalidad , Resultado del TratamientoRESUMEN
The primary objective of this study is to functionally characterize and provide molecular evidence of large neutral amino acid transporter (LAT1) in human derived prostate cancer cells (PC-3). We carried out the uptake of [3H]-tyrosine to assess the functional activity of LAT1. Reverse transcription-polymerase chain reaction (RT-PCR) analysis is carried out to confirm the molecular expression of LAT1. [3H]-tyrosine uptake is found to be time dependent and linear up to 60 min. The uptake process does not exhibit any dependence on sodium ions, pH and energy. However, it is temperature dependent and found maximal at physiological temperature. The uptake of [3H]-tyrosine demonstrates saturable kinetics with K(m) and V(max) values of 34 ± 3 µM and 0.70 ± 0.02 nanomoles/min/mg protein, respectively. It is strongly inhibited by large neutral (phenylalanine, tryptophan, leucine, isoleucine) and small neutral (alanine, serine, cysteine) but not by basic (lysine and arginine) and acidic (aspartic and glutamic acid) amino acids. Isoleucine-quinidine (Ile-quinidine) prodrug generates a significant inhibitory effect on [3H]-tyrosine uptake suggesting that it is recognized by LAT1. RT-PCR analysis provided a product band at 658 and 840 bp, specific to LAT1 and LAT2, respectively. For the first time, this study demonstrates that LAT1, primarily responsible for the uptake of large neutral amino acids, is functionally active in PC-3 cells. Significant increase in the uptake generated by Ile-quinidine relative to quinidine suggests that LAT1 can be utilized for enhancing the cellular permeation of poor cell permeable anticancer drugs. Furthermore, this cell line can be utilized as an excellent in vitro model for studying the interaction of large neutral amino acid conjugated drugs with LAT1 transporter.